This invention relates to noise reduced computer fan cooling systems.
Personal computers and generic boxes housing electronic components are conventionally cooled by fans mounted to their back panels that blow air across their respective components and transfer heat through convection.
The design trend towards smaller enclosures packing more computing power in less space has increased the amount of heat generated per unit area and consequently has required more effective and reliable cooling. Failure to provide adequate cooling can result in electronic component or peripheral failure, the loss of valuable computing time, and wasted resources in recovering lost data. It is therefore more cost efficient to provide a given box with the requisite cooling initially than to repair and retrofit. However, it is also important to provide cooling without introducing acoustic noise that could diminish system efficiency. System acoustic noise generally takes two forms: mechanical noise and aerodynamic noise.
Mechanical noise is generated from the vibration of moving parts such as fans and disk drives. Aerodynamic noise is generated from turbulent airflow across and in the vicinity of the fan blades. The design and implementation of grommets or other dampening devices for minimizing mechanical noise is well known in the art. Techniques of minimizing aerodynamic noise are less well known. However, while less well known and less critical than the techniques for minimizing mechanical noise they are still important for optimizing system efficiency.
In general, aerodynamic noise generated by cooling fans is a function of the type of flow in the region surrounding the fan blades, flow velocity, fan blade shape, number of fan blades and the shape of the duct in which the fan is housed.
Many different approaches have been tried to minimize cooling fan noise. These approaches try to minimize noise contributions by modifying at least one of the aforementioned parameters. However, a first problem known in the art is that changing flow velocity and type of flow can result in less cooling and it would be desirable to change flow characteristics to minimize noise without diminishing cooling capacity.
It is known in the art to provide a grille at an airflow entrance for the fan both for human safety and for minimizing radiated electromagnetic noise. A second problem known in the art is that an airflow grille with grill openings small enough to minimize both radiated electromagnetic noise and human contact with rotating fan blades can decrease the efficiency of the fan. This efficiency decrease can result from at least two factors. (1) The airflow grille produces back-pressure on the fan, so that operation of the fan is strained and the fan can be subject to extra wear. (2) The airflow grille produces turbulence, so that operation of the fan is less efficient and airflow over the systems or equipment is less efficient at cooling.
Accordingly, it would be advantageous to provide a cooling system and a method for operating a cooling system, which has relatively reduced noise and is relatively efficient and inexpensive. This advantage is achieved in an embodiment of the invention in which a laminar flow duct modifies flow characteristics by separating a set of cooling fans from an airflow grille. Thus, back pressure on the fan is reduced and laminar flow through the fan and over the systems or equipment is improved.
The invention provides a cooling system and a method for operating a cooling system, which has relatively reduced noise and is relatively efficient and inexpensive. A set of cooling fans operates in conjunction with an airflow grille and a laminar flow duct, so as to reduce the amount of aerodynamic noise, and to block dust and other foreign objects. A laminar flow duct separates the cooling fans from the airflow grille, so as to reduce back pressure on the fan and improve laminar flow through the fan and over the systems or equipment. Additionally, the laminar flow duct acts to reduce electromagnetic noise.
In a preferred embodiment, the laminar flow duct defines a Venturi opening, so as to draw airflow into the cooling fans from a region adjacent to the laminar flow duct. The Venturi opening allows the cooling fans to cool a secondary set of systems or equipment, such as a set of disk drives or other equipment that need relatively minimal cooling effect.